conditional statment in prompt

Question

I'm working on providing a user with two different pictures depending on the right username/password. I'm having a prompt popup for the user to give the username/password and after providing the right credentials the login picture should appear and if the credentials are wrong the logout picture should appear. I am using the getElementById to change accordingly. At this moment the prompt shows up, but there is no picture showing.

<img src="user_in.PNG" id="user_in_id" hidden>
<img src="user_out.PNG" id="user_out_id" hidden>

<script> 
      
     var person = prompt("Please enter your name", ""); 
     var password = prompt("Please enter your password", "");
     if (person == "admin" && password =="admin") {
        alert("Welcome, You are now Logged in");
        document.getElementById("user_in_id");

      }else
        alert("wrong username or password");
        document.getElementById("user_out_id");
      
</script>